Emissions from diesel-powered locomotives contribute to air pollution and have significant health and environmental effects. Nitrogen oxides (NOx), hydrocarbons (HC) and particulate matter (PM) are the major components of such emissions that significantly impact the environment. NOx is a significant component of smog and acid rain and can combine with HC to form ground-level ozone, which is another significant component of smog. Ozone can be hazardous to people by damaging lung tissue and causing congestion. PM can cause headaches, eye and nasal irritation and lung inflammation.
The 1990 Clear Air Act amendments mandated the EPA to establish emissions standards for a variety of previously unregulated sources, including locomotives. Consequently, the EPA promulgated a comprehensive program that included limits on the various emissions components from diesel-powered locomotives. For locomotives manufactured between Jan. 1, 1973 and Jan. 1, 2000 the level of NOx must be 9.5 grams per brake-horsepower-hour (g/bhp-hr) or less, PM must be 0.6 g/bhp-hr or less, HC must be 1.00 g/bhp-hr or less. These maximum levels also apply to any locomotive built and rebuilt during the same time frame. For locomotives manufactured between Jan. 1, 2002 to Jan. 1, 2004 the level of NOx emitted must be 7.4 g/bhp-hr or less, PM must be 0.45 g/bhp-hr or less and HC must be 0.55 g/bhp-hr or less. Finally, for locomotives manufactured after Jan. 1, 2005 the level of NOx emitted must be 5.5 g/bhp-hr or less, PM must be 0.20 g/bhp-hr or less and HC must be 0.30 g/bhp-hr or less.
Unfortunately, most diesel-powered locomotives currently operating emit NOx, PM and HC in quantities exceeding these EPA established limits. Thus, there is a need for a diesel-powered locomotive that can provide the same or more power while emitting less NOx, PM and HC.
The present invention provides a diesel engine that can generate more power while generating fewer emissions. The diesel engine comprises a cylinder assembly that includes a head operable to remove combusted fuel from the combustion chamber and a piston comprising an igniter operable to ignite fuel injected into a combustion chamber and a top section operable to agitate the air in the combustion chamber. The head allows the engine to generate more power with fewer emissions by permitting more combusted fuel to flow out of the combustion chamber, and thus, more fresh air to flow into the combustion chamber. More fresh air in the combustion chamber further reduces the amount of unburned fuel remaining after combustion. Thus, the amount of PM in the engine""s emissions is reduced. The igniter allows the engine to generate more power with fewer emissions by igniting the fuel quickly after it is injected into the combustion chamber. This reduces the time between injection and combustion of the fuel in the combustion chamber and thus, the amount of NOx produced during combustion. In addition, injection of the fuel can commence when the piston is closer to TDC and thus more power can be generated. The top section allows the engine to generate more power with fewer emissions by quickly mixing the fuel and air as the fuel is injected into the combustion chamber. Thus, the igniter can ignite the fuel quickly after the fuel is injected, and carbon build-up from unburned fuel in the combustion chamber can be reduced.
In one aspect of the invention, the igniter radiates heat to the fuel as the fuel is injected across the igniter""s top surface. Consequently the igniter can be made of any material, such as Inconel(copyright) 625 or 750X, that will retain more heat than the remaining structure of the piston. Furthermore, the igniter can use some of the heat generated by previous combustion events to ignite the fuel in subsequent combustion events.
In another aspect of the invention, the igniter can be releasably attached to the piston to allow one to remove and install different igniters having different shapes and sizes and made from different materials. By modifying these one can change the performance characteristics of the engine to match changing conditions or as desired. In addition, the igniter can include grooves for agitating the air in the combustion chamber in a plane perpendicular or substantially perpendicular to the piston""s movement toward the head. This helps mix the fuel and air quickly so that the igniter can quickly ignite the fuel.
In another aspect of the invention, the top section of the piston can be formed to agitate the air in a direction substantially toward and away from the head, for example, circulating the air in a plane substantially parallel to the direction the piston travels. For example, the piston can include a piston bowl and squish land. The piston bowl can include a bowl diameter, a transition radius, a bowl radius and a bowl surface all sized and located relative to a piston diameter and piston longitudinal axis. The squish land can include an inside edge and a squish surface also sized and located relative to a piston diameter and piston longitudinal axis.
In another aspect of the invention, the head includes a primary chamber that receives a flow of combusted fuel through at least two exhaust ports and directs the flow out of the head, and at least one passage that receives a flow of combusted fuel through at least one other exhaust port and directs the flow out of the head. In addition, the at least one passage can include a narrow section operable to accelerate the flow of combusted fuel through the passage.